The present invention relates to vehicles.
In particular, the present invention relates to vehicles which are propelled by way of at least one endless track guided around a pair of end rolls.
In particular, the present invention relates to structure of endless tracks of the above type which enable the vehicle to execute turns. Thus, when the vehicle executes a turn one side of the endless track contracts while the other side expands enabling the track to assume a curvature corresponding to the turning of the vehicle.
In general with vehicles of the above type where an endless track is guided around a pair of end rolls, if the vehicle should turn to the right, for example, then the right ends of the end rolls approach each other while the left ends are displaced farther apart from each other, and the endless track must contract along its right side and expand along its left side when the vehicle executes such a turn to the right. Of course the opposite operations take place when the vehicle executes a turn toward the left in that at this time the left side of the endless track will contract and the right side thereof will expand.
Experience has shown that when steering a vehicle in the above manner, although a number of substantial advantages are achieved, it is important to provide the endless track with special properties creating special problems in the construction of the endless track.
It is to be understood that the endless track of the invention can form the only track of a vehicle or can be combined with additional tracks which are arranged one beside the other and/or consecutively.
Attempts have already been made to provide constructions of the above general type where the endless track will not slip with respect to the end rolls or the equivalent of the latter. For example in U.S. Pat. No. 3,565,198 there is shown a construction where sprocket wheels are provided to form a construction similar to end rolls around which an endless track is guided, with these sprocket wheels having teeth which are received in mating openings of the endless track elements to prevent slippage between the track and the end rolls. However, there is nothing in the latter patent to indicate the significance of this feature, and it has been found from experience that a construction where sprocket wheels extend into openings of track elements has inherent problems which do not provide the possibility of preventing slipping with substantially cylindrical end rolls which are highly desirable.
As the endless track of a vehicle of the above type travels onto a swinging end roll, with the latter being swung in order to steer the vehicle, the endless track necessarily assumes an oblique position resulting from the fact that one side of the endless track slips while the other side has a good grip or engagement on the end roll, while in the case of partial turns of relatively large radius there is a tendency of the tension and traction forces of the endless track to straighten the track at a part thereof which extends between a lateral steadying wheel and the end roll, so that for this latter reason also the endless track tends to arrive in an oblique condition onto the end roll. These latter operations result in a number of undesirable effects which include an undesirable increase in the turning radius, imposing a high stress on the endless track and preventing a relatively high speed of travel when executing turns. As a result of the above undesirable effects, an endless track such as one which is made of rubber will acquire objectionable "bagging" portions during execution of turns, which is to say portions of the track will ripple and become undesirably corrugated, preventing the load from being uniformly distributed and preventing the vehicle from carrying out smooth turns at relatively high speeds.
Thus, when a vehicle of the above general type executes a turn which is larger than that provided at the minimum radius of curvature of the endless track, the track necessarily encounters a tendency to contract at its side which is directed toward the center of the turn and a tendency to expand at the opposite side, providing inside contractions and outside dilations while the remainder of the track remains substantially straight. As a result when executing a fairly wide turn at a relatively high speed the several elements of the track strike against each other as well as against the lateral supports for the endless track, and the result is creation of impacts which must be absorbed by the remainder of the track structure such as a structure for limiting the extent to which the length of the track can increase. In addition when executing turns as a result of the above actions there is a lateral dragging force at the lateral supports for the track.
Moreover, with known constructions reliance is made on the end rolls rather than the track to achieve the desired results.